The coastal waters from Washington to California are home to a community of killer whales known as the southern resident orcas. 

In 2005, after their population precipitously declined, they wound up on the federal endangered species list. The orcas' food sources and habitat have been threatened by pollution and traffic from busy shipping lanes.

The National Oceanic and Atmospheric Administration has been studying these massive mammals all this time, and their newly released research shows this community is still struggling to survive.

Brad Hanson, a biologist with NOAA's fishery center said the whales are threatened by a complex set of factors, from diminishing food sources, to contaminants and complications from living in congested waters, that seem to be affecting their reproductive success and overall health.

The southern resident orcas preferred food source, chinook salmon, has been increasingly threatened by environmental factors leading to a likely calorie reduction in the orcas' diet. That coupled with the extra energy expended to avoid ships and communicate in noisy waters could be imperiling the orcas.

Hanson said NOAA will continue to focus on improving watersheds where chinook salmon live and trying to control for contaminants, such as agricultural waste that affects salmon swimming in waters in California's Central Valley, which are an increasing food source for these whales.